Heating device having resin layer over core metal of heating roller

ABSTRACT

A heating device is used in an image forming apparatus. In the heating device, a resin layer is provided between a core metal of a fixing roller and a ball bearing. The resin layer is adhered to the core metal so as to obviate a noise, caused by a rubbing of the resin layer against a ball bearing, which is otherwise produced when the resin layer is provided as a separate part. Between the resin layer and the ball bearing, a material of the resin layer is selected and the resin layer is configured to have a rough surface with a coefficient of dynamic friction of the surface of the resin which is a predetermined value, and thereby minimizing the production of the noise.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This patent application claims priority to Japanese PatentApplication No. 2000-362912, filed on Nov. 29, 2000, and the entirecontents are incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a heating device in which aheating roller heated at high temperature is brought into contact with amember to be heated, and more particularly to the heating device used ina fixing process of a toner image in an electrophotographic printingprocess and an image forming apparatus, such as a printer, a copier,etc., having the heating device in a fixing section thereof.

[0004] 2. Discussion of the Background

[0005] In an electrophotographic printing process, an electrostaticlatent image formed on a surface of a photoconductive element isdeveloped with toner. The developed toner image is transferred onto atransfer sheet. Then a fixing process is performed to fix the tonerimage onto the transfer sheet. In the fixing process, the toner image isfixed onto the transfer sheet by at least heat and pressure. In a fixingdevice, the transfer sheet having the toner image is conveyed whilebeing sandwiched by a fixing roller and a pressure roller. The fixingroller is heated to a high temperature. The pressure roller is drivenwhile being press-contacted with the fixing roller. The toner image onthe transfer sheet is then fixed while the transfer sheet is conveyed bythe fixing roller.

[0006] In recent years, an attempt has been made to shorten a period oftime required for a warm-up operation and to process an image at highspeed in an image forming apparatus, in which an electrophotographicprinting process is performed, such as a printer, a copier, etc.Corresponding to the above-described attempt, an attempt has been madeto heat a fixing roller to higher temperature and convey a transfersheet at higher speed in the fixing device. A resinoid sliding bearing,which is obtained at low cost, may be employed as a bearing of thefixing roller. However, a disadvantage to the sliding bearing is that adriving torque increases in the early stages of use and especially overthe lapse of time, and that its durability decreases due to adeformation caused by a heat stress, when the fixing roller rotates athigh speed.

[0007] Thus, an attempt has been made to use a ball bearing instead ofthe sliding bearing. The driving torque decreases when the ball bearingis used. A motor, which is smaller than that is used when the slidingbearing employed, is then used, resulting in a reduction in costs.Because the fixing roller is formed into a drum shape having a heaterinside, it is advantageous that the fixing roller has a decreasedthickness to shorten a period of time required for a warm-up operation.However, if the thickness of the fixing roller is decreased, a largeamount of deformation appears. Thus, a wrinkle of a transfer sheet tendsto occur.

[0008] To obviate the above-described inconvenience, a value of“thickness/outer diameter” of an image region (i.e., a central portionof the fixing roller through which a transfer sheet is conveyed) of thefixing roller needs to be in a predetermined range according to a sizeof a diameter of the fixing roller. Conventionally, an outer diameter ofa portion of the fixing roller, which is supported by a bearing providedto a main body of the apparatus, is smaller than that of the imageregion thereof.

[0009] When a ball bearing is employed to shorten a warm-up time andprocess an image at high speed, heat is conducted to the ball bearing ifthe ball bearing directly contacts a core metal of a fixing roller.Thus, the ball bearing is heated to high temperature, resulting in adecreased lifetime of the ball bearing. Further, during a warm-upoperation, heat dissipates from the both ends of the fixing roller whichare supported by the ball bearing. Thus, a temperature of the endportions of the fixing roller tends to decrease, resulting in a faultyfixing. Therefore, an insulating resin layer (i.e., a bush) or a ceramicmember is provided between the fixing roller and the ball bearing toobviate the above-described behavior of heat, thereby preventing theabove-described inconvenience.

[0010] However, a noise is produced when the resin layer or ceramicmember is rubbed against the core metal and ball bearing if the resinlayer or ceramic member is conventionally provided as a separate part.The production of the noise may be reduced using a grease, however, afluorine grease for a high-temperature is expensive. When the ceramicmember is used, an insulating effect is enhanced, however, resulting notonly in an increase in costs but in a further production of the noise.

[0011] The below-described problem needs to be solved when the ballbearing is adopted. As described above, the thickness of the fixingroller is determined such that the value of “thickness/outer diameter”of the image region is in the predetermined range. However, thethickness of the supported portion of the fixing roller needs to beadjusted based on the determined thickness of the image region of thefixing roller to obviate a deformation of the fixing roller and anoccurrence of a wrinkle of a transfer sheet. Conventionally, an innerdiameter of the supported portion of the fixing roller is set to a valueequal to that of the inner diameter of the image region. Therefore, whena design change is made in the thickness of the supported portion, anouter diameter of the supported portion is eventually changed.

[0012] Thus, a general-purpose ball bearing is not used, and acustomized ball bearing that fits to the modified outer diameter of thesupported portion of the fixing roller is required. Conventionally, theouter diameter of the supported portion is smaller than that of theimage region. The supported portion is then supported by a bearingprovided to a main body of the apparatus. Thus, a replacement of thefixing roller with new one is not easily performed without dismantling arelating component.

SUMMARY OF THE INVENTION

[0013] The present invention has been made in view of theabove-mentioned and other problems and addresses the above-discussed andother problems.

[0014] The present invention advantageously provides a novel imageforming apparatus having a heating device used in a fixing operation ofa toner image in an electrophotographic printing process, wherein aproduction a noise, caused by a rubbing of the resin layer (which isprovided between a core metal of a fixing roller and a ball bearing tosuppresses a conduction of heat from the fixing roller to the ballbearing) against the ball bearing and core metal of the fixing roller,is obviated.

[0015] According to an example of the present invention, when aclearance is created between the resin layer and the ball bearing, amaterial of the resin layer is selected and the resin layer isconfigured to have a rough surface so as to have a coefficient ofdynamic friction of the resin surface in a predetermined value. Athickness of a supported portion of the fixing roller is determinedbased on a thickness of an image region of the fixing roller to preventa deformation of the fixing roller. An inner diameter of the supportedportion of the fixing roller is smaller than that of the image region sothat an outer diameter of the supported portion of the fixing roller isnot changed even if the thickness of the supported portion of the fixingroller is changed so that a general-purpose ball bearing is used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more complete appreciation of the present invention and many ofthe attendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

[0017]FIG. 1 is a schematic drawing illustrating a construction of aprinter as an image forming apparatus;

[0018]FIG. 2 is a schematic drawing illustrating a construction of afixing device employed in the image forming apparatus in FIG. 1;

[0019]FIG. 3 is a schematic drawing illustrating a construction of afixing roller as an example of a heating device;

[0020]FIGS. 4A and 4B are drawings illustrating a sectional view of thefixing roller in which a resin layer is adhered to a core metal of thefixing roller;

[0021]FIG. 5 is a drawing illustrating a transverse sectional view ofthe fixing roller in FIGS. 4A and 4B;

[0022]FIG. 6 is a drawing illustrating a perspective view of a ballbearing used in the example illustrated in FIGS. 4A and 4B;

[0023]FIG. 7 is a drawing illustrating a vertical sectional view of theball bearing and the resin layer that includes a rough surface;

[0024]FIG. 8A is a drawing illustrating a polishing operation of thefixing roller 14; and

[0025]FIG. 8B is a drawing illustrating a fixing roller having a leveldifference portion that forms a right angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring now to the drawings, wherein like reference numeralsdesignate identical or corresponding parts throughout the several views,FIG. 1 is a schematic drawing illustrating a construction of a printeras an image forming apparatus according to an example of the presentinvention. The image forming apparatus includes a fixing device whichincludes a heating device of the present invention. FIG. 2 is aschematic drawing illustrating a construction of the fixing device.Referring to FIG. 1, the construction and operation of the image formingapparatus is described below along a flow of a transfer sheet on whichan image is formed. The transfer sheet fed from a sheet feeding device 5is conveyed to a photoconductive element 4 (which is belt-shaped in thisexample) on a surface of which an image (i.e., an electrostatic latentimage) is formed. The registration roller 6 conveys the transfer sheetby adjusting the time such that the transfer sheet is in preciseregister with the image formed on the surface of the photoconductiveelement 4. The photoconductive element 4 is driven in a clockwisedirection. Devices performing a respective electrophotographic printingprocess are arranged along a run of the photoconductive element 4. Thesurface of the photoconductive element 4 is charged by a charger 2. Alaser writing optical system 1 irradiates the surface of the chargedphotoconductive element 4 with a scanning beam modulated according toimage data so as to form an electrostatic latent image thereon. Theelectrostatic latent image is developed into a visible image with tonerby a developing device 3. The visible image is then transferred onto atransfer sheet by a transfer charger 7. The transfer sheet, which isbrought into a press-contact with the photoconductive element 4 in atransfer process, is separated from the photoconductive element 4 at acurvature of the photoconductive element 4. The transfer sheet is thenconveyed to a fixing device 8 so that the image is fixed. Thus, thetransfer sheet is discharged to a sheet discharging tray 9. Residualcharge remaining on the photoconductive element 4 is discharged by adischarging lamp 10.

[0027] Residual toner remaining on the surface of the photoconductiveelement 4 is removed by a cleaning device 11. An AC (AlternativeCurrent) and DC (Direct Current) power required for the above-describedseries of operations is supplied from a power source 12.

[0028] The fixing device 8 is described below in details. The fixingdevice 8 fixes a toner image, which has been transferred onto a transfersheet from the photoconductive element 4 in an image transfer process,by applying at least heat and pressure. The fixing device 8 is heated toa high temperature. The fixing device 8 includes a fixing roller 14(i.e., a heating roller) and a pressure roller 16. The fixing roller 14rotatably drives and the pressure roller 16 is rotatably driven by therotation of the fixing roller 14 while press-contacting with the fixingroller 14. The transfer sheet having the toner image is conveyed througha nip formed between the fixing roller 14 and pressure roller 16. Thus,the toner image is fixed onto the transfer sheet 20. As illustrated inFIG. 2, the fixing device 8 includes the fixing roller 14, the pressureroller 16, a cleaning pad 18, a switching pick 17, a pressure spring 15,and a fixing device inlet guide plate 19. The fixing device 8 furtherincludes a gear (not shown) to drive the fixing roller 14, a bearing(not shown) for the fixing roller 14, and a thermistor (not shown).

[0029] The fixing roller 14 is employed in the heating device of thepresent invention. FIG. 3 is a schematic drawing illustrating aconstruction of the heating device. Both end portions of the fixingroller 14 are rotatably supported by a ball bearing 21. A driving gear14 g is provided to one end of the fixing roller 14 from outside of theball bearing 21. The fixing roller 14 is driven via the driving gear 14g. A diameter of a portion of a circumferential surface of the fixingroller 14 which is supported by the ball bearing 21 (i.e., a supportedportion) is equal to that of the circumferential surface of an imageregion 9 thereof (i.e., a central portion of the fixing roller 14through which a transfer sheet is conveyed). Namely, the diameter of thecircumferential surface of the portion of the fixing roller 14 which issupported by the ball bearing 21 is not smaller than that of thecircumferential surface of the fixing roller 14 of the image region,unlike a conventional fixing roller. Thus, the fixing roller 14 ispulled out in an axial direction by removing retaining rings 14 r, whichare provided approximately at both edges of the fixing roller 14 toregulate a movement of the fixing roller 14 in the axial direction. Areplacement of the fixing roller 14 with new one is easily performedwithout removing parts provided to a main body of the apparatus, such asthe ball bearing 21. The fixing roller 14 includes a core metal made ofiron (i.e., STKM11, STKM12) or aluminum alloy having a diameter of 16 mmto 40 mm and a length of 350 mm to 410 mm. A degree of a deformation ofthe fixing roller 14, which is caused when a pressure is applied,differs according to a size of a diameter of the fixing roller 14 (i.e.,the larger the diameter, the greater the degree of the deformation evenif a thickness is the same). Therefore, a thickness of the fixing roller14 is set to a value in a range of thickness/outer diameter fromapproximately 8/1000 to approximately 20/1000 (for example, the diameteris 30 mm, the thickness is 0.24 mm to 0.6 mm). It is preferable that thethickness is set in a range of approximately 8/1000 to approximately14/1000 when the core metal is made of iron and when the core metal ismade of aluminum alloy, the thickness is set in a range of approximately10/1000 to approximately 20/1000. When the value of “thickness/outerdiameter” is small, the degree of the deformation of the fixing roller14 becomes great. Thus, a wrinkle of a transfer sheet tends to begenerated. To the contrary, when the value of “thickness/outer diameter”is large, a comparatively long period of time is required before thefixing roller 14 is heated to a required temperature for a fixingoperation, resulting in a longer warm-up time for the fixing operation.

[0030] The transfer sheet 20 is conveyed by a rotation of the fixingroller 14. In the example of the present invention, an explanation isgiven below based on a linear velocity of the conveyed transfer sheet 20is in a range of about 100 mm/s to about 130 mm/s. The pressure roller16 includes an elastic layer over a core substrate. The diameter of thepressure roller 16 is, for example, 30 mm. A thickness and length of theelastic layer is set to about 5.5 mm and about 316 mm, respectively. Theelastic layer is either a sponge-formed or a solid-formed (i.e.,non-sponge). The used fixing roller 14 includes a core metal made ofiron (i.e., STKM12) having an outer diameter of 30 mm. A thickness of animage region of the fixing roller 14 is 0.3 mm. A value of“thickness/outer diameter” is 10/1000. Another used fixing rollerincludes the core metal made of aluminum alloy (i.e., A5052). The outerdiameter is 30 mm and the thickness of the image region is 0.45 mm. Thevalue of “thickness/outer diameter” is 15/1000. A length of the fixingroller 14 is 365 mm. According to the example, a warm-up time isshortened to 10 to 15 seconds when a heater 13 has 700 to 800 watts ofpower.

[0031] It is advantageous to use the ball bearing 21 as a bearing tosupport the fixing roller 14 when the fixing roller 14 is rotated at ahigh speed. When the fixing roller 14 rotating at a high speed issupported by a resin sliding bearing, a driving torque is increased inthe early stages of use, and especially over the lapse of time. Thedriving torque is not significantly increased when the ball bearing 21is used. In addition, a motor, which is smaller than that is employedwhen the resin sliding bearing is used, can be used because the drivingtorque is reduced, resulting in a reduction in costs. However, if a ballbearing directly contacts a core metal of a fixing roller, theinconvenience described in the section of “Discussion of the Background”is caused due to a conduction of heat. A resin layer (i.e., a resinmember) is provided between the core metal of the fixing roller and theball bearing for heat insulation. However, a noise is caused when theresin layer is rubbed against the core metal of the fixing roller or theball bearing if the resin layer is provided as a separate part.

[0032] An example of a fixing roller, in which the rubbing noise causedby the resin layer provided between the core metal of the fixing rollerand the ball bearing is eliminated, is described below. In this example,the resin layer is adhered to the core metal of the fixing roller suchthat the resin layer is not rubbed against the core metal of the fixingroller, thereby obviating a production of the noise. FIG. 4A is adrawing illustrating a vertical sectional view of the fixing roller 14in which the resin layer 22 is adhered to the core metal 24 of thefixing roller 14. In FIG. 4A, both end portions of the fixing roller 14are supported by a ball bearing 21. FIG. 4B is a drawing illustrating anenlarged view of a part of the fixing roller 14. The driving gear 14 gillustrated in FIG. 3 is omitted in FIG. 4A. FIG. 5 is a drawingillustrating a transverse sectional view of the fixing roller 14. In theexample illustrated in FIG. 4, an outer diameter of a portion of thefixing roller 14 which is supported by the ball bearing 21 is slightlylarger than that of the image region of the fixing roller 14 by 0.2 mmto 0.6 mm. FIG. 4B is a drawing illustrating an enlarged view of a leveldifference formed in the portion of the fixing roller 14 where thediameter of the circumferential surface changes.

[0033] As illustrated in FIGS. 4A, 4B, and 5, a resin layer 22 isadhered to a core metal 24 via a primer layer 23. The resin layer 22 islayered on both portions of circumferential surfaces of the fixingroller, namely, the portion where the circumferential surface issupported by the ball bearing 21 (i.e., a supported portion) and theportion of the circumferential surface that is the image region. This isbecause the same surface layer at (which has a necessary property (i.e.,mainly release effect) for the surface that contacts a transfer sheet)as that is layered on the image region is layered on the circumferentialsurface of the supported portion of the fixing roller 14. However, aresin having a high insulative property may be layered only on thecircumferential surface of the supported portion of the fixing roller14.

[0034] Another example of the present invention is described below. Inthe example, a production of a noise caused by a rubbing of the resinlayer 22 (which is constructed integrally with the core metal 24 of thefixing roller 14) against the ball bearing 21 is obviated. Asillustrated in FIG. 4A, a clearance of 0.04 mm to 0.15 mm is createdbetween the ball bearing 21 and the resin layer 22 because the fixingroller 14 expands with temperature. FIG. 6 is a drawing illustrating aperspective view of the ball bearing 21. As illustrated in FIG. 6, theball bearing 21 includes an outer ring 21 o and an inner ring 21 i. Theresin layer 22 of the fixing roller 14 may not be rubbed against theinner ring 21 i of the ball bearing 21 because the outer ring 210 o isfixed to a main body of the apparatus and the inner ring 21 i rotates.However, a noise may be produced in fact because (1) the above-describedclearance is created, and (2) the torque of the fixing roller 14 variesin a case where a transfer sheet is conveyed between the fixing roller14 and the pressure roller 16, and in a case where no transfer sheet isconveyed therebetween. Then, a coefficient value that suppresses theproduction of the noise is examined while paying particular attention toa coefficient of dynamic friction of the surface of the resin layer 22.It is observed that the resin layer 22 smoothly slides over the innerring 21 i when the coefficient of dynamic friction of the resin layer 22surface is set to 0.2 to 0.5 (when the fixing roller 14 moves at thespeed of 50 mm/s having a load of 7 Kgf/cm2), thereby suppressing theproduction of the noise. Methods and materials to achieve apredetermined coefficient of dynamic friction are described below.

[0035] As described above, a resin having a high insulative property maybe layered only on the circumferential surface of the supported portionof the fixing roller 14. However, if the resin that is different fromthat layered on the image region is used, a cost is increased. Thus, theresin layer 22 including a fluororesin is integrally layered on both theimage region and supported portion of the fixing roller 14. Thefluororesin is layered mainly to have a release effect. This fluororesinlayer 22 is adhered to the core metal 24 of the fixing roller 14 withthe primer layer 23 (i.e., an adhesion layer). In a fluororesin, amaterial that has a coefficient of dynamic friction of 0.2 to 0.5 (whenthe fixing roller 14 moves at the speed of 50 mm/s having a load of 7Kgf/cm2), such as a perfluoroalkoxy resin, tetrofluoroethylene resin, amixture of these two resins, or resins produced by adding an additive ora reinforcement agent (such as carbon and glass fiber) to respectiveresins may be used. The surface of the resin layer 22 is made as roughas possible while the above-described coefficient of dynamic friction ismaintained in a proper range. FIG. 7 is a drawing illustrating avertical sectional view of the ball bearing 21 and the resin layer 22that includes a rough surface. As illustrated in FIG. 7, the resin layer22 has roughness on the surface that contacts the inner ring 21 i of theball bearing 21. The surface roughness (Rz) of the resin layer 22 is setto 3 to 12 μm. With this arrangement, an area of a contacting portion ofthe resin layer 22 (i.e., fluororesin) with the ball bearing 21 isreduced, thereby enhancing a insulation effectiveness. Further, thesurface of the contacting portion of the resin layer 22 is not polishedat all or is polished only once without having a finish polish,resulting in a reduction in costs.

[0036] As described above referring to FIGS. 4A and 4B, the outerdiameter of the portion of the fixing roller 14 which is supported bythe ball bearing 21 is larger than that of the image region, such thatthe fixing roller 14 is removed in the axial direction, therebysimplifying a replacement of the fixing roller 14 with new one. Thus, alevel difference is formed between the supported portion and the imageregion in the circumferential surface of the fixing roller 14. If thelevel difference forms a right angle similar to a different levelportion 14 c illustrated in FIG. 8B, a polishing tape may be snagged onthe different level portion 14 c when polishing the surface of thefixing roller 14 with the polishing tape.

[0037]FIG. 8A is a drawing illustrating a polishing operation of thefixing roller 14. As illustrated in FIG. 8A, the polishing of thesurface of the fixing roller 14 is performed by moving a reel of thepolishing tape in a direction indicated by an arrow “A” while thepolishing tape is brought into contact with the surface of the fixingroller 14 which rotates in a direction indicated by an arrow “B”. Inthis polishing operation, an inconvenience, such as the polishing tapeis snagged on the different level portion 14 c or the fluororesin of thecorner of the different level portion 14 c is scraped may be caused. Inorder to avoid the above-described inconvenience, the different levelportion is tapered instead of being formed having a right angle so thatthe polishing of the fixing roller 14 is easily performed using thepoling tape.

[0038]FIG. 4B shows the enlarged tapered different level portion. Withthe tapered different level portion, the scrape of the fluororesin isminimized. In addition, as illustrated in FIG. 4B, a corner of thetapered different level portion is configured to have a curve 15R havinga radius of 0.5 mm to 1.5 mm, thereby obviating the scrape of thefluororesin of the corner of the different level portion.

[0039] As described above, an occurrence of a wrinkle of a transfersheet in a fixing operation is prevented when a value of“thickness/outer diameter” is set to a predetermined range. However, ifthe value is applied to the supported portion of the fixing roller 14,the fixing roller 14 is deformed, thereby generating the wrinkle of thetransfer sheet in the fixing operation.

[0040] Another example of the present invention is described. In theexample, a proper value of a thickness of the supported portion of thefixing roller 14 is described. The proper value of the thickness of thesupported portion of the fixing roller 14 is determined based on athickness of the image region of the fixing roller 14. The value in arange of one and half to three times (i.e., 1.5 to 3 times) thethickness of the image region is selected as the value of the thicknessof the supported portion. For example, when the thickness of the imageregion is 0.45 mm, the thickness of the supported portion is set to 0.9mm to 1.0 mm.

[0041] When the above-described value is adopted, the deformation of thefixing roller 14 and the occurrence of the wrinkle of the transfer sheetin the fixing operation is prevented. In addition, the time required fora warm-up operation of the fixing roller 14 is shortened. An outerdiameter of the image region is determined by a linear velocity of atransfer sheet and a composition of a gear that transmits a drivingtorque to the fixing roller 14. Thus, the thickness of the image regionis consequentially decided to achieve a shortened warm-up time of thefixing roller 14. Then, an inner diameter of the core metal 24 of theimage region is determined based on these values. However, if the propervalue of thickness of the supported portion of the fixing roller 14 isdecided based on the thickness of the image region thereof as describedabove, the outer diameter of the supported portion may be changed due toa design change in the thickness of the image region and the supportedportion. Thus, it may happen that a general-purpose ball bearing (i.e.,an inner diameter of a ball bearing is fixed) can not be used, and anexpensive customized ball bearing is required. Hence, the inner diameterof the supported portion of the fixing roller 14 is made smaller thanthat of the image region thereof so that the outer diameter of thesupported portion is not changed even if the thickness of the supportedportion is changed. Then, the general-purpose ball bearing may be usedbecause the outer diameter of the supported portion of the fixing roller14 is not changed, thereby avoiding an increase in costs.

[0042] Considering the above-described conditions, a numerical valueactually adopted to a fixing roller is described below, referring toFIGS. 4A and 4B. (The outer diameter of the supported portion “D1”—theouter diameter of the image region “D2”)/2=0.1 mm to 0.3 mm. The lengthof the tapered different level portion in an axial direction “1”=0.5 mmto 2.0 mm. (The inner diameter of the image region “d2”−the innerdiameter of the supported portion “d1”)/2=0.3 mm to 0.5 mm. The lengthbetween the thick portion “A” and the thin portion “B” in the axialdirection “L” is set to 1 mm to 3 mm such that the thickness does notsteeply change in the direction of the length.

[0043] Obviously, numerous additional modifications and variations ofthe present invention are possible in light of the above teachings. Itis therefore to be understood that within the scope of the appendedclaims, the present invention may be practiced otherwise than asspecifically described herein.

What is claimed as new and is desired to be secured by Letters Patent ofthe United States is:
 1. A heating device, comprising: a heating rollerconfigured to contact a heated member; and a ball bearing configured tosupport the heating roller, wherein a resin layer is adhesively providedto a surface of a supported portion of a core member of the heatingroller which is supported by the ball bearing, and wherein a roughnessof a contact portion of the surface of the resin layer that contacts theball bearing is set to a roughness predetermined value in which aproduction of a noise caused by a rubbing of the resin layer against theball bearing is substantially suppressed and an insulating effect isenhanced.
 2. The heating device according to claim 1, wherein acoefficient of dynamic friction of the surface of the resin layer is setto a friction predetermined value in which the production of the noisecaused by the rubbing of the resin layer against the ball bearing issuppressed.
 3. The heating device according to claim 1, wherein theresin layer layered over the supported portion of the heating roller isintegrally-layered over the surface of the contacting portion of thecore member with the heated member.
 4. The heating device according toclaim 1, wherein an outer diameter of the supported portion of theheating roller is at least as large as an outer diameter of thecontacting portion of the heating roller with the heated member.
 5. Theheating device according to claim 4, wherein when the outer diameter ofthe supported portion of the heating roller is larger than the outerdiameter of the contacting portion of the heating roller with the heatedmember, a portion of the supported portion of the heating roller that isconnected to the contacting portion of the heating roller with theheated member forms a tapered portion.
 6. The heating device accordingto claim 5, wherein a corner of an end of the tapered portion of theheating roller is configured to include a circular curve.
 7. The heatingdevice according to claim 1, wherein a first thickness of the supportedportion of the heating roller is larger than a second thickness of thecontacting portion of the heating roller with the heated member.
 8. Theheating device according to claim 7, wherein the first thickness of thesupported portion of the heating roller is determined such that an outerdiameter of the supported portion of the heating roller is maintained ina thickness predetermined value when the first thickness of thesupported portion of the heating roller is larger than the secondthickness of the contacting portion of the heating roller with theheated member.
 9. A heating device, comprising: a heating rollerconfigured to contact a heated member; and a ball bearing configured tosupport the heating roller, wherein a first outer diameter of asupported portion of the heating roll er that is supported by the ballbearing is at least as large as a second outer diameter of a contactedportion of the heating roller that contacts the heated member.
 10. Theheating device according to claim 9, wherein when the first outerdiameter of the supported portion of the heating roller is larger thanthe second outer diameter of the contacting portion of the heatingroller with the heated member, a portion of the supported portion of theheating roller that is connected to the contacting portion of theheating roller with the heated member forms a tapered portion.
 11. Theheating device according to claim 10, wherein a corner of an end of thetapered portion of the heating roller is configured to include acircular curve.
 12. A heating device, comprising: a heating rollerconfigured to contact a heated member; and a ball bearing configured tosupport the heating roller, wherein the heating roller is configuredsuch that a first thickness of a supported portion of the heating rollerthat is supported by the ball bearing is larger than a second thicknessof a contacted portion of the heating roller that contacts the heatedmember.
 13. The heating device according to claim 12, wherein the firstthickness of the supported portion of the heating roller is determinedsuch that an outer diameter of the supported portion of the heatingroller is maintained in a thickness predetermined value when the firstthickness of the supported portion of the heating roller is larger thanthe second thickness of the contacting portion of the heating rollerwith the heated member.
 14. An image forming apparatus, comprising: animage bearing member configured to form a latent image on a heatedmember; and a heating device configured to perform a fixing operationincluding, a heating roller configured to contact the heated member; anda ball bearing supporting the heating roller, wherein a resin layer isadhesively provided to a surface of a supported portion of a core memberof the heating roller which is supported by the ball bearing, andwherein a roughness of a contact portion of the surface of the resinlayer that contacts the ball bearing is set to a roughness predeterminedvalue in which a production of a noise caused by a rubbing of the resinlayer against the ball bearing is suppressed and a insulating effect isenhanced.
 15. An image forming apparatus, comprising: is an imagebearing member configured to form a latent image on a heated member; anda heating device configured to perform a fixing operation including, aheating roller configured to contact the heated member; and a ballbearing supporting the heating roller, wherein a first outer diameter ofa supported portion of the heating roller that is supported by the ballbearing is at least as large as a second outer diameter of a contactportion of the heating roller that contacts the heated member.
 16. Animage forming apparatus, comprising: an image bearing member configuredto form a latent image; and a heating device configured to perform afixing operation including, a heating roller configured to contact aheated member; and a ball bearing supporting the heating roller, whereinthe heating roller is configured such that a first thickness of asupported portion of the heating roller that is supported by the ballbearing is larger than a second thickness of a contacting portion of theheating roller that contacts the heated member.
 17. A method forobviating a production of a noise caused by a rubbing of a core memberof a heating roller against a ball bearing that supports a portion ofthe core member of the heating roller in a heating device, the methodcomprising the steps of: providing a resin layer between the supportedportion of the core member of the heating roller and the ball bearingsupporting the supported portion of the core member of the heatingroller; and setting a roughness of a surface of the resin layer thatcontacts the ball bearing to a roughness predetermined value.
 18. Amethod for enhancing a replaceability of a heating roller in a heatingdevice, the method comprising the steps of: providing the heating rollerto contact a heated member; and providing a ball bearing to support aportion of a core member of the heating roller, wherein an outerdiameter of a supported portion of the heating roller that is supportedby the ball bearing is at least as large as an outer diameter of acontact portion of the heating roller that contacts the heated member.19. A method for obviating a deformation of a heating roller in aheating device, the method comprising the steps of: providing theheating roller to contact a heated member; and providing a ball bearingto support a portion of a core member of the heating roller, wherein theheating roller is configured such that a first thickness of a supportedportion of the heating roller that is supported by the ball bearing islarger than a second thickness of a contact portion of the heatingroller that contacts the heated member.
 20. A heating device,comprising: means for contacting a heated member; and means forsupporting the heating roller for contacting, wherein a resin layer isadhesively provided to a surface of a supported portion of a core memberof the means for contacting which is supported by the means forsupporting, and wherein a roughness of a resin surface of the resinlayer that contacts the means for supporting is set to a roughnesspredetermined value in which a production of a noise caused by a rubbingof the resin layer against the is means for supporting is substantiallysuppressed and an insulating effect is enhanced.
 21. The heating deviceaccording to claim 20, wherein a coefficient of dynamic friction of acontact portion of the resin layer is set to a friction predeterminedvalue in which the production of the noise caused by the rubbing of theresin layer against the means for supporting is suppressed.
 22. Theheating device according to claim 20, wherein the resin layer layeredover the supported portion of the means for contacting isintegrally-layered over the surface of the contacting portion of thecore member with the heated member.
 23. The heating device according toclaim 20, wherein a first outer diameter of the supported portion of theheating roller is at least as large as a second outer diameter of acontacting portion of the heating roller means with the heated member.24. The heating device according to claim 23, wherein when the firstouter diameter of the supported portion of the means for contacting islarger than the outer diameter of the contacting portion of the heating.25. The heating device according to claim 24, wherein a corner of an endof the tapered portion of the means for contacting is configured toinclude a circular curve. means,
 26. The heating device according toclaim 20, wherein a first thickness of the supported portion of themeans for contacting is larger than a second thickness of the contactingportion of the means for contacting with the heated member.
 27. Theheating device according to claim 26, wherein the first thickness of thesupported portion of the means for contacting is determined such that anouter diameter of the supported portion of the heating roller means ismaintained in an outer diameter predetermined value when the firstthickness of the supported portion of the means for contacting is largerthan the second thickness of the contacting portion of the heating meansfor contacting with the heated member.
 28. A heating device, comprising:means for contacting a heated member; and means for supporting the meansfor contacting, wherein a first outer diameter of a supported portion ofthe means for contacting that is supported by the means for supportingis at least as large as a second outer diameter of a contacted portionof the means for contacting that contacts the heated member.
 29. Theheating device according to claim 28, wherein when the first outerdiameter of the supported portion of the means for contacting is largerthan the outer diameter of the contacting portion of the means forcontacting with the heated member, a portion of the supported portion ofthe means for contacting that is connected to the contacting portion ofthe means for contacting with the heated member forms a tapered portion.30. The heating device according to claim 28, wherein a corner of an endof the tapered portion of the means for contacting is configured toinclude a circular curve.
 31. A heating device, comprising: means forcontacting a heated member; and means for supporting the means forcontacting, wherein the means for contacting is configured such that afirst thickness of a first portion of the means for contacting that issupported by the means for supporting is larger than a second thicknessof a second portion of the means for contacting that contacts the heatedmember.
 32. The heating device according to claim 31, wherein the firstthickness of the supported portion of the means for contacting isdetermined such that an outer diameter of m the supported portion of themeans for contacting is maintained in a predetermined value when thefirst thickness of the supported portion of the means for contacting islarger than the second thickness of the contacting portion of the meansfor contacting with the heated member.
 33. An image forming apparatus,comprising: image bearing means for forming a latent image on a heatedmember; and heating means for performing a fixing operation including,means for contacting the heated member; and means for supporting themeans for contacting, wherein a resin layer is adhesively provided to asurface of a supported portion of a core member of the means forcontacting which is supported by the means for supporting, and wherein aroughness of the surface of the resin layer that contacts the means forsupporting is set to a roughness predetermined value in which aproduction of a noise caused by a rubbing of the resin layer against themeans for supporting is suppressed and an insulating effect is enhanced.34. An image forming apparatus, comprising: image bearing means forforming a latent image on a heated member; and heating means forperforming a fixing operation including, means for contacting the heatedmember; and means for supporting the means for contacting, wherein afirst outer diameter of a supported portion of the means for contactingthat is supported by the means for supporting is at least as large as asecond outer diameter of a contact portion of the means for contactingthat contacts the heated member.
 35. An image forming apparatus,comprising: image bearing means for forming a latent image on a heatedmember; and heating means for performing a fixing operation including,means for contacting the heated member; and means for supporting themeans for contacting, wherein the means for contacting is configuredsuch that a first thickness of a first portion of the means forcontacting that is supported by the means for supporting is larger thana second thickness of a second portion of the means for contacting thatcontacts the heated member.